Implication of the Oral Bacteria on the Onset of Infective Endocarditis

In this study, we attempted to clarify the implication of the oral bacteria on the onset of infective endocarditis (IE).  In the first experiment, oral bacteria could be found in the blood from 27 of the 47 patients (57.4%) with IE.  Furthermore, 29of the patients (61.7%) showed possible oral bacterial foci causing the bacteremia, and 8 of the patients (17.0%) received the oral surgery or the dental treatment accompanying bleeding.  In the second experiment, we isolated the oral bacteria (Staphylococci and Streptococci) from the 27 patients with IE or with high risk for the onset of IE, and determined the susceptibility for several anti-biotics.  Ninety two point three percent of the bacteria showed susceptibility against penicillin G and its derivatives.  In the third experiment, we identified the bacterial species isolated from oral cavity and blood in nine patients with IE by determining the DNA sequence of the 16S rRNA.  The bacterial species isolated from blood in the patients with IE were Staphylococcus epidermidis or Streptococcus mitis group, which usually existed in the oral cavity.  DNA sequence of the 16S rRNA in the bacteria (Staphylococcus epidermidis) from blood in one patient was completely identical to that from oral cavity.  In three patients, although DNA sequence from blood was not completely identical to that from oral cavity, the species (Streptococcus mitis group) of the bacteria from blood and oral cavity were identical.  These results suggest that oral Staphylococci and Streptococci play a crucial role on the onset of IE.  Moreover, complete removal of the oral bacterial foci, daily oral care, and the administration of the large amount of penicillin before the oral surgery or the dental treatment accompanying bleeding might be effective to prevent the onset of IE.